Add the class variable and the class itself in Ractor::IsolationError

Author: etiennebarrie

bootstraptest/test_ractor.rb

@@ -1022,7 +1022,7 @@ def initialize
 }
 
 # cvar in shareable-objects are not allowed to access from non-main Ractor
-assert_equal 'can not access class variables from non-main Ractors', %q{
+assert_equal 'can not access class variables from non-main Ractors (@@cv from C)', %q{
   class C
     @@cv = 'str'
   end
@@ -1041,7 +1041,7 @@ class C
 }
 
 # also cached cvar in shareable-objects are not allowed to access from non-main Ractor
-assert_equal 'can not access class variables from non-main Ractors', %q{
+assert_equal 'can not access class variables from non-main Ractors (@@cv from C)', %q{
   class C
     @@cv = 'str'
     def self.cv

variable.c

@@ -1197,7 +1197,7 @@ IVAR_ACCESSOR_SHOULD_BE_MAIN_RACTOR(ID id)
 
 #define CVAR_ACCESSOR_SHOULD_BE_MAIN_RACTOR() \
   if (UNLIKELY(!rb_ractor_main_p())) { \
-      rb_raise(rb_eRactorIsolationError, "can not access class variables from non-main Ractors"); \
+      rb_raise(rb_eRactorIsolationError, "can not access class variables from non-main Ractors (%s from %"PRIsVALUE")", RSTRING_PTR(rb_id2str(id)), klass); \
   }
 
 static inline void